How much interest will she earn in 3 years?

At the end of each year, the balance is (1 +0.13) times the amount at the beginning of the year. After 3 years, the balance will be
.. $90*1.13^3 = $129.86

Of that balance, $90 is the original deposit, so the interest earned is
.. $129.86 -90.00 = $39.86

Idon’t know what the answer is i wish i could